A system and method is disclosed for helping determine a condition of selected tissue of a patient based on a set of thermal images of the selected tissue acquired over a time period. The image set has image regions with corresponding characteristics indicative of a temperature condition of an associated part of the selected tissue, which had been subjected to a thermal challenge during part of the image acquisition time period. Feature values are determined based on the characteristics of selected image regions. A classifier is applied to the features to provide an indication of the condition of the selected tissue, such as indicating a likelihood of malignancy.